(color online) The operating principle of the sine-wave gating single-photon detector(SG-SPD). DC: DC power source; APD: avalanche photodiode; Att: variable attenuator; BSF: band-stop filter; LPF: low-pass filter. APD’s model is JDS Uniphase X00408052-005. In our experiment, the laser is a pulse laser with external trigger function, the full width at half maximum of the laser pulse is 80 ps, the delayer’s adjusting precision is 10 ps, the gain of the amplifier is 20 dB, and the bandwidth of oscilloscope is 8 GHz. The dotted line represents the light connections, accordingly, the solid line represents the electrical connections. (a) Schematics of the SG-SPD, in which the APD under testing is cooled electrically to −50 °C, the bias DC voltage is 49.7 V, the detection efficiency η is 11.7% with a corresponding dark count rate of 18.6 kHz, and the discrimination level of the avalanche signal after 20-dB amplification is 66 mV in our experiment. (b) The sine wave gating signal with frequency of ω. Here we set ω = 1 GHz, and correspondingly we choose a band-stop filter with 10MHz bandwidth and the stop-band central frequencies of 1 GHz, 2 GHz, and 3 GHz, while the low-pass filter with a cut-off frequency of 3.5 GHz. (c) Schematics of a single photon signal captured by the oscilloscope.